When a shuttle valve is used in a fluid system, the two inlet ports of the shuttle valve may be connected to different sources of fluid pressure. The different sources of fluid pressure may be at different pressure levels, and each of the pressure levels may increase or decrease with time. The shuttle poppet of the shuttle valve closes fluid pressure communication between the lower pressure source inlet port and the outlet port. The shuttle poppet also establishes and maintains fluid pressure communication between the higher pressure source inlet port and the outlet port. As used herein, the term fluid pressure communication with reference to two or more surfaces or volumes means that such surfaces or volumes are in relatively open fluid flow communication and/or at substantially similar pressure levels under normal operating conditions when such surfaces or volumes are in the described configuration. The term leakage communication with reference to two or more surfaces or volumes means that such surfaces or volumes are in relatively restricted fluid flow communication and/or at substantially dissimilar pressure levels under normal operating conditions when such surfaces or volumes are in the described configuration. The terms inlet port or inlet and outlet port or outlet do not preclude fluid flow in a reverse direction such that an inlet becomes an outlet or an outlet becomes an inlet, unless the context otherwise so requires.
The shuttle poppet, which may also be referred to as a valve member, may have a first at rest position and a second at rest position. In the first at rest position, the lower fluid pressure source may be connected to the first inlet port and the higher fluid pressure source may be connected to the second inlet port. In this configuration, a first valve surface of the shuttle poppet closes fluid pressure communication between the lower pressure source first inlet port and the outlet port while fluid pressure communication between the higher pressure source second inlet port and the outlet port is established and maintained. In the second at rest position, the relative pressure levels of the first and second inlet ports may reverse, so that the first inlet port may be at the higher pressure level and the second inlet port may be at the lower pressure level. In this configuration, a second valve surface of the shuttle poppet closes fluid pressure communication between the lower fluid pressure source second inlet port and the outlet port while fluid pressure communication between the higher fluid pressure source first inlet port and the outlet port is established and maintained. In this manner, the inlet port that is at the higher pressure level is connected to the outlet port.
The shuttle poppet of the shuttle valve is moved between its first and second at rest positions in response to fluid pressure. More specifically, the shuttle poppet is moved in response to the fluid pressure differential between the first inlet port and the second inlet port. Some shuttle valves may include biasing members to prevent movement of the shuttle poppet until a predetermined pressure differential between the inlet ports is reached.
The pressure differential between the two inlet ports is generally the main determinant of the acceleration and velocity of travel of the shuttle poppet. If a high pressure differential between the inlet ports builds rapidly to move the shuttle poppet from one of its at rest position to its other at rest position, the shuttle poppet may tend to accelerate relatively quickly and move at a rapid velocity and then abruptly stop when its other at rest position is reached. Depending upon the pressure levels, the pressure level differentials, the rate of change of those differentials, the valve and pipe sizes and lengths, the elasticity or capacitance of the system, the resulting speed of movement of the shuttle poppet and other factors, these conditions may produce shock or water hammer in the system as is well known. Also, if the pressure differential between the first and second inlet ports is relatively small and/or it changes in direction rapidly and/or frequently, the shuttle poppet may oscillate back and forth more than necessary for proper system functioning.
Prior art U.S. Pat. No. 7,243,671 discloses a chatter resistant shuttle valve that includes a valve body with a shuttle valve member or poppet movably mounted inside. Dampening or cushioning chambers are provided which dampen movement of the shuttle valve member in each direction.
Shuttle valves of this type may be used in any of several known applications. One such application is in drilling fields in which drilling rigs drill wells into the ground (including underwater surfaces) for locating and connecting to underground fluid resources such as oil or natural gas or for locating and connecting to underground chambers to pump fluids into the chambers for storage. In these uses, the shuttle valve may be used as a component in a blow out preventer circuit that is designed to change fluid flow paths and prevent over pressure conditions that might blow out piping or other components during instances of rapid high pressure build up in the well. A blow out preventer is any fluid circuit that operates in any application to change the path of fluid flow in response to fluid pressure change. A drilling field blow out preventer is any such blow out preventer that is used in connection with well drilling into the ground.